Having a sectional sofa slide apart as you are sitting or laying on it can be very annoying and potentially dangerous. Fortunately, there are several easy ways you can secure the sections so they hold together instead of sliding apart.
Ask the delivery person or salesperson, if it is a new sectional sofa, to see if there is hardware included with the sofa. Sometimes it is included, but they forget to give it to you if you do not ask. Check the bottom of the sofa, new or old, to see if there is a small package attached to it with the hardware inside.
Buy a product designed to hold sectional sofas together, such as the Sofa Snap. Screw the bracket onto the frame on the bottom of one section of the sofa and the fork onto the other section.
Create your own do-it-yourself tool to hold the sections together using hook and eyes from the hardware store. Get heavy duty hooks and eyes so they do not bend out of shape under the pressure. Screw the eye onto the frame on the bottom or the back of one section of the sofa and the hook onto the other section. Push the two sections together and attach the hook into the eye.
Go low-tech and buy two heavy duty cable ties. Push the sections together. Wrap the cable ties around the feet of each section, pull tightly and secure.